labelfont, fieldfont and linkdefs only change most of the font appearances, well, how to change the rest? E.g. tagline and description remain the way they were, some hyperlinks do the same... Am I right to assume that those three before mentioned guys are not the (only) global font setting strings?
Those should work for all field labels (but not checkbox labels) and all field data (except some link fields). There are no more
global font settings. The other stuff should be changed locally.
How to I add custom fields? I found something like <customfieldlabel field="my field"/> but nothing about this fella:<? my field/>
Adds a checkbox field named "Find in better quality":
<custom field="Find in better quality"/>
<customfieldlabel field="Find in better quality"/>
# Can I change the colour of those little buttons that expand lists?
No
Can I add dots to the "actors (vast space) role" vast space?
No
Can I recolour the left view?
Yes, in Tools -> Preferences -> Appearance
# Is there a list of all available fields and their names?
Not really, but you can take a look at existing skins (actually all the fields are already there).
* Is there a script that could do stuff like "add 'something' to field A"? Or: can I create templates for new movies? E.g. if I add a TV recording the template already contains "TV" @ quality and "DVD5" @ mediatype etc?
No